In this handout provided by the National Oceanic and Atmospheric Administration (NOAA) from the GOES-East satellite, four separate weather system (L-R) Halong, Genevieve, Iselle, and Julio are tracked in the Pacific Ocean off the west coast of the United States.
Handout/Getty Images

Hurricanes Iselle is forecast to hit Hawaii on Thursday, followed by Hurricane Julio this weekend. The storms are the first hurricanes to land in Hawaii in more than two decades, and the rush to prepare is overtaking the islands. The biggest impact will likely be felt on the Big Island, with hurricane effects starting midday today. Already, sustained 80 mph winds are blowing about 300 miles east of Hilo -- in the Big Island city, skies are calm, but overcast. While Hawaii’s mountainous terrain and high volcanos may provide some buffer to the storm, there may still be violent winds, rain, and flooding on the Big Island. Oahu (which includes Honolulu) will likely avoid hurricane conditions, but will still face a tropical storm.

What is causing these stormy conditions in Hawaii? How are the islands preparing for the hurricane? How will Hurricanes Iselle and Julio develop in the next few days?